Insulating wall board sizing



United States Patent 3,138,480 INSULATING WALL BOARD SIZING Christian F. Girard, Ottawa, Ontario, Canada, assignor to Canadian International Paper Company, Montreal, Quebec, Canada, a corporation of Canada No Drawing. Filed Sept. 27, 1961, Ser. No. 141,016 9 Claims. (Cl. 117-65.2)

This invention relates to fiber board, More particularly, it relates to improving the surfaces of insulating wall board made from Wood fibers.

It is well known to make wall board from wood fibers ranging in density from as low at 12 lbs. per cubic foot to as high as 24 lbs. per cubic foot. In some instances, most of the wood used consists of poplar, some of which is converted to the fibrous form by grinding on conventional stones and some of which is converted by chipping and steaming, followed by disc refining. Some slush pulp in the form of rejects from newsprint mills can be mixed in with the virgin furnish, as can some of the dust which is returned from the board finishing operation. These various pulps are then mixed in the ratio required for the type of board being produced, are screened, and have a wax emulsion and alum added thereto for water resistance. When needed, a cooked flour to increase the fiexural strength can also be added as described in co-pending application Serial No. 41,249, filed July 7, 1960, now abandoned.

One manner of forming the fiber board involves the use of an Oliver filter-type forming machine, though a Fourdrinier machine can also be used. The pulp is reduced to about 1% consistency and is flowed through a head box and into the Oliver vat, where the sheet is formed on the filter to the required thickness. This wet mat, at about 80% moisture content, is then transferred to a series of suction rolls whereby the moisture content is progressively reduced to about 60%. The mat then goes into steam-heated driers wherein it becomes fiber board having a moisture content of about 2 to 4%, Gas-heated kilns could, of course, be used in place of the steam-heated driers. The board is then cut up into the required dimensions for processing into tiles, e.g., about 52 by 52".

Although the surfaces of the fiber board thus produced are fairly smooth, it has been found that they can be made smoother for purposes of painting, gluing, etc., by sanding or the use of a hot-rolling preceded by a waterspraying of the board surfaces. Both methods are used to achieve an evening out of the small hills and valleys, e.g., wire markings, caused by stock formation during the manufacturing process. However, it has been found that sanding becomes quite costly and does not produce results sufficiently satisfactory in terms of smoothness. It has also been found that spraying the surface fibers with water prior to hot-rolling is not altogether suitable, since it fails to achieve adequate binding of the surface fibers or sealing of the surfaces.

It is an object of the present invention, therefore, to achieve a smooth finish on the surface of fiber board useful for insulating wall boards or the like, so as to improve its appearance, to prepare more perfectly its front surface for painting, to prepare more perfectly its back surface for gluing, and, more generally, to give the entire board heightened dust-free properties.

It is a further object of the present invention so to treat the front and back surfaces of fiber board as to achieve the desired results without appreciable scorching of the surfaces when they are subjected to hot roll temperatures of up to about 750 F., without sticking of the surfaces to the heated rolls at operational speeds of about 100 feet per minute or to each other when the fiber board is cut into tiles and stacked.

In accordance with the present invention, fiber board 3,138,480 Patented June 23, 1964 is treated on its surfaces with a size, for example, on a reverse coater after it is cut into tiles and before it is hotrolled. The product of this process has substantially unscorched, non-tacky, and unblistered surfaces which are semi-glazed, colorless, and well-sealed for purposes of painting, gluing, etc. The usual water-base coatings can be applied economically to produce attractive wall board products in the form of panels, planks, and decorative tiles. Such coatings can include water-based paints of the polyvinyl acetate emulsion or latex type applied with a flow coater or other conventional means, as well as waterbased paints of butadiene styrene, acrylic, polyvinylidene chloride latex types, alkyd emulsions, and protein paints of the casein and soya types. In addition, commercially available oil-based flat colored paints, as well as waterbased paints, can be employed on the fiber board of the present invention, without resort to sealers, by use of brushes, roller coaters, or spray guns and there result improved hold-out, hiding, flow, and, levelling of the pigmented paints.

A size developed in accordance with the present invention is, for example, one in which water, carboxymethylcellulose, colloidal silica, and polyvinyl acetate are mixed and applied at from about 8 to 10 grams per square foot of fiber board per side or surface prior to a hot-rolling thereof at about 700 F. In a preferred formula, 60.24 U.S. gallons of hot water, 5 lbs. of medium viscosity sodium carboxymethylcellulose, 50 lbs, of Nalcoag 1050 (a commercially available product containing 50% colloidal silica solids), and 12.04 U.S. gallons of Latex D-Sl (a commercially available 55% polyvinyl acetate emulsion) are employed.

What is claimed is:

1. In the process of manufacturing insulating board, a first step of sizing the surfaces of the fiber board with a composition consisting essentially of water, carboxymethylcellulose, colloidal silica, and polyvinyl acetate and a second step of hot-rolling the surfaces in which the composition is proportioned to about 60.24 U.S. gallons of water, about 5 pounds of medium viscosity carboxymethylcellulose, about 50 pounds of colloidal silica containing about 50% solids, and about 12.04 U.S. gallons of polyvinyl acetate emulsion containing about 55% solids.

2. The process of claim 1 in which the hot-rolling step is conducted at a temperature of up to about 750 F.

3. The process of claim 1 in which the hot-rolling step is conducted at a speed of up to feet of board per minute.

4. The process of claim 1 in which the composition is applied at a rate of about 8 to 10 grams per square foot of the insulating board.

5. A sizing composition for insulating board, the composition consisting essentially of water, carboxymethylcellulose, colloidal silica, and polyvinyl acetate in proportions of about 60.24 U.S. gallons of Water, about 5 pounds of medium v iscgsity carboxymethylcellulose, about 50 pounds of coll dal silica containing about 50% solids, and about 12.04 U.S. gallons of polyvinyl acetate emulsion containing about 55 solids.

6. Insulating board having disposed on at least one of its surfaces a dried sizing composition consisting essentially of water, carboxymethylcellulose, colloidal silica, and polyvinylacetate in proportions of about 60.24 U.S. gallons of water, about 5 pounds of medium viscosity carboxymethylcellulose, about 50 pounds of colloidal silica containing about 50% solids, and about 12.04 U.S. gallons of polyvinyl acetate emulsion containing about 55% solids.

7. The product of claim 6 in which the composition is disposed in a sizing of about 8 to 10 grams per square foot of the product.

8. Insulating board having disposed on at least one of its surfaces a hot-rolled sizing composition consisting essentially of water, carboxymethylcellulose, colloidal silica, and polyvinyl acetate in proportions of about 60.24 US. gallons of Water, about 5 pounds of medium viscosity carboxymethylcellulose, about 50 pounds of colloidal silica containing about 50% solids, and about 12.04 US. gallons of polyvinyl acetate emulsion containing about 55% solids.

9. The product of claim 8 in which the composition is disposed in a sizing of about 8 to 10 grams per square foot of the product.

References Cited in the file of this patent UNITED STATES PATENTS Deney Sept. 26, 1950 Cowgill May 29, 1951 Iler May 6, 1958 Emblem et al Aug. 28, 1962 

1. IN THE PROCESS OF MANUFCTURING INSULATING BOARD, A FIRST STEP OF SIZING THE SURFACES OF THE FIBER BOARD WITH A COMPOSITION CONSISTING ESSENTIALLY OF WATER, CARBOXYMETHYLCELLULOSE, COLLOIDAL SILICA, AND POLYVINYL ACETATE AND A SECOND STEP OF HOT-ROLLING THE SURFACES IN WHICH THE COMPOSITION IS PROPORTIONED TO ABOUT 60.24 U.S. GALLONS OF WATER, ABOUT 5 POUNDS OF MEDIUM VISCOSITY CARBOXYMETHYLCELLULOSE, ABOUT 50 POUNDS OF COLLOIDAL SILICA CONTAINING ABOUT 50% SOLIDS, AND ABOUT 12.04 U.S. GALLONS OF POLYVINYL ACETATE EMULSION CONTAINING ABOUT 55% SOLIDS. 